Method of manufacturing and device for manufacturing membrane-catalyst assembly

ABSTRACT

An object of the present invention is to provide, in the manufacture of a membrane-catalyst assembly including a polymer electrolyte membrane and a catalyst layer bonded to the polymer electrolyte membrane, a method that achieves both the relaxation of thermocompression bonding conditions and the improvement of adhesion between the catalyst layer and the electrolyte membrane with high productivity. A main object of the present invention is to provide a method of manufacturing a membrane-catalyst assembly including an electrolyte membrane and a catalyst layer bonded to the electrolyte membrane, the method including a liquid application step of applying a liquid to a surface of the catalyst layer before bonding, and a thermocompression bonding step of bonding, to the electrolyte membrane, the catalyst layer to which the liquid is applied by thermocompression bonding.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a memberincluding a polymer electrolyte membrane and a catalyst layer bonded tothe polymer electrolyte membrane, that is, a membrane-catalyst assembly,which is used in electrochemical devices such as polymer electrolytefuel cells, as well as to a device for manufacturing a membrane-catalystassembly.

BACKGROUND ART

Fuel cells are a kind of power generator from which electric energy isextracted by electrochemical oxidation of a fuel such as hydrogen ormethanol, and have recently attracted attention as a clean energysource. Above all, polymer electrolyte fuel cells have a low standardoperating temperature of around 100° C. and a high energy density.Therefore, polymer electrolyte fuel cells are expected to be widelyapplied to relatively small distributed power generation facilities aswell as to power generators for mobile objects such as automobiles andships. Polymer electrolyte membranes (hereinafter sometimes simplyreferred to as “electrolyte membranes”) are key materials of polymerelectrolyte fuel cells. In recent years, use of polymer electrolytemembranes in hydrogen infrastructure-related equipment such as solidpolymer electrolyte membrane water electrolyzers and electrochemicalhydrogen pumps is also under consideration.

In the application of the polymer electrolyte membrane to suchelectrochemical devices, a member including an electrolyte membrane anda catalyst layer bonded to the electrolyte membrane is used. A typicalexample of such a member is a catalyst layer-attached electrolytemembrane including an electrolyte membrane and a catalyst layer formedon a surface of the electrolyte membrane.

For example, the following method is known as a method of manufacturinga catalyst layer-attached electrolyte membrane. First, a catalystsolution is applied to a surface of a sheet made ofpolytetrafluoroethylene (PTFE) or the like and having excellentreleasability, which is used as a temporary base material. Then, thesolvent in the applied catalyst solution is evaporated to form a driedcatalyst layer. Further, the dried catalyst layer and an electrolytemembrane are thermocompression-bonded together using a flat press or aroll press to transfer the catalyst layer to the polymer electrolytemembrane. Finally, the temporary base material is separated from thecatalyst layer transferred to the polymer electrolyte membrane. Themethod of transferring the once dried catalyst layer to the electrolytemembrane is employed because if the solvent in the catalyst solutionadheres to the electrolyte membrane, the solvent may swell theelectrolyte membrane to cause wrinkles, and the electrolyte membrane maybe deformed.

When the dried catalyst layer is thermocompression-bonded to theelectrolyte membrane, however, the adhesion between the catalyst layerand the electrolyte membrane may be insufficient unless the catalystlayer and the electrolyte membrane are pressed at high temperature andhigh pressure for a long time. Meanwhile, if the catalyst layer and theelectrolyte membrane are subjected to harsh thermocompression bondingconditions in order to improve the adhesion therebetween, the catalystlayer may be compressed and deformed, resulting in reduced gasdiffusivity and poor power generation performance, or the electrolytemembrane may be subjected to thermal stress and damaged, resulting inpoor durability. However, if the temperature and pressure of thepressing are simply reduced in order to reduce the damage to thecatalyst layer and the electrolyte membrane, the pressing time needs tobe increased to compensate for the reduction, so that the productivityis greatly reduced.

Therefore, various techniques have been proposed in order to achievesatisfactory adhesion between the electrolyte membrane and the catalystlayer while relaxing the thermocompression bonding conditions. Forexample, the following methods have been proposed: a method ofsemi-drying a catalyst solution, and bonding a catalyst layer to anelectrolyte membrane with a slight amount of a solvent componentremaining in the catalyst layer as in Patent Document 1; and a method ofapplying a solution containing a binder resin having proton conductivityto a surface of a dried catalyst layer, and bonding the catalyst layerto an electrolyte membrane before the solution is completely dried as inPatent Document 2.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent No. 4240272

Patent Document 2: Japanese Patent Laid-open Publication No. 2013-69535

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the method described in Patent Document 1, it is possibleto ensure satisfactory adhesion between the electrolyte membrane and thecatalyst layer under relaxed thermocompression bonding conditionswithout causing wrinkles in the electrolyte membrane by leaving thesolvent component in the catalyst layer to such an extent that only thejoint surface of the electrolyte membrane to the catalyst layer may besoftened. However, it is difficult to control the drying so that theamount of the remaining solvent will be uniform on the entire surface ofthe catalyst layer while partially removing the solvent in the catalystsolution by heating. Therefore, due to the difference in the degree ofdrying in the surface of the catalyst layer, products having a highinterfacial resistance between the electrolyte membrane and the catalystlayer, and products having wrinkles due to deformation of theelectrolyte membrane or cracks in the surface of the catalyst layer aremixed, and the products have unstable quality. In addition, the amountof the remaining solvent has a narrow margin, and the reduction ofproductivity may lead to an increase in cost. Further, since the solventcomposition of the catalyst solution is limited, it is difficult toflexibly change the type of catalyst layer.

According to the method described in Patent Document 2, the solutioncontaining a binder resin having proton conductivity is applied to thejoint surface of the catalyst layer to the electrolyte membrane, and thecatalyst layer is bonded to the electrolyte membrane before the solutionis completely dried. Thus, the solution serves as an adhesive, and themethod can ensure satisfactory adhesion between the electrolyte membraneand the catalyst layer even at low temperature and low pressure.However, use of the solution containing a binder resin having protonconductivity for bonding the electrolyte membrane to the catalyst layerincreases the manufacturing cost. Further, the method also has thefollowing problems: the binder resin is a component similar to that ofthe electrolyte membrane, so that the binder resin substantiallyincreases the thickness of the electrolyte membrane and increases theelectric resistance; and the organic solvent in the solution remainingat the interface between the electrolyte membrane and the catalyst layermay deteriorate the power generation performance.

An object of the present invention is to provide, in the manufacture ofa member including a polymer electrolyte membrane and a catalyst layerbonded to the polymer electrolyte membrane (the member is hereinafterreferred to as a “membrane-catalyst assembly”), a manufacturing methodthat achieves both the relaxation of thermocompression bondingconditions (pressing pressure, pressing temperature, and pressing time)and the improvement of adhesion between the catalyst layer and theelectrolyte membrane with high productivity.

Solutions to the Problems

The present invention for solving the above-mentioned problems providesa method of manufacturing a membrane-catalyst assembly including anelectrolyte membrane and a catalyst layer bonded to the electrolytemembrane, the method including a liquid application step of applying aliquid to a surface of the catalyst layer before bonding, and athermocompression bonding step of bonding, to the electrolyte membrane,the catalyst layer to which the liquid is applied by thermocompressionbonding.

The present invention also provides a device for manufacturing amembrane-catalyst assembly including an electrolyte membrane and acatalyst layer bonded to the electrolyte membrane, the device includinga liquid applicator that applies a liquid to a surface of the catalystlayer before bonding, and a thermocompression bonding unit that bonds,to the electrolyte membrane, the catalyst layer to which the liquid isapplied by thermocompression bonding.

Effects of the Invention

According to the present invention, it is possible to manufacture amembrane-catalyst layer assembly while achieving both the relaxation ofthermocompression bonding conditions (pressing pressure, pressingtemperature, and pressing time) and the improvement of adhesion betweenthe catalyst layer and the electrolyte membrane with high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing a schematic configuration of a device formanufacturing a membrane-catalyst assembly according to a firstembodiment of the present invention.

FIG. 2 is a side view showing a schematic configuration of the devicefor manufacturing a membrane-catalyst assembly according to a secondembodiment of the present invention.

FIG. 3 is a side view showing a schematic configuration for forming afirst catalyst layer in the device for manufacturing a membrane-catalystassembly according to a third embodiment of the present invention.

FIG. 4 is a side view showing a schematic configuration for forming asecond catalyst layer in the device for manufacturing amembrane-catalyst assembly according to the third embodiment of thepresent invention.

FIG. 5 is a side view showing a schematic configuration for forming afirst catalyst layer in the device for manufacturing a membrane-catalystassembly according to a fourth embodiment of the present invention.

FIG. 6 is a side view showing a schematic configuration for forming asecond catalyst layer in the device for manufacturing amembrane-catalyst assembly according to the fourth embodiment of thepresent invention.

FIG. 7 is a side view showing a schematic configuration for illustratinga different method for separating temporary base materials in the devicefor manufacturing a membrane-catalyst assembly according to the firstembodiment of the present invention.

FIG. 8 is a side view showing a schematic configuration for illustratingheat shield plates in the device for manufacturing a membrane-catalystassembly according to the first embodiment of the present invention.

EMBODIMENTS OF THE INVENTION

The operations of the present invention may include the following,although the present invention is not limited to the following in anyway. In the thermocompression bonding step, the electrolyte membrane andthe catalyst layer are compressed with a liquid applied to the jointsurface of the catalyst layer to the electrolyte membrane, so that theair present at the interface is removed, and substantially the liquidalone is present between the electrolyte membrane and the catalystlayer. When heat is further applied in this state, the liquid evaporatesand the interface is evacuated, so that the adhesion between thecatalyst layer and the electrolyte is improved. Further, since theelectrolyte membrane comes into contact with the liquid and softens, theadhesion between the catalyst layer and the electrolyte membrane isfurther improved. Since the electrolyte membrane is held by thecompression in the thermocompression bonding while being in contact withthe liquid, the occurrence of swelling is prevented. Further, the liquidevaporated at the interface passes through the pores of the catalystlayer having a porous structure, and is discharged to the outside of themembrane-catalyst assembly.

As used herein, the term “membrane-catalyst assembly” is a term thatmeans not only a so-called catalyst layer-attached electrolyte membraneincluding an electrolyte membrane and a catalyst layer formed on asurface of the electrolyte membrane, but also any laminate having ajoint surface between an electrolyte membrane and a catalyst layer. Forexample, a membrane-electrode assembly, which includes a so-called gasdiffusion electrode including a base material made of gas-permeablecarbon paper or the like and a catalyst layer formed on one surface ofthe base material, and an electrolyte membrane bonded to the gasdiffusion electrode, is also one aspect of the “membrane-catalystassembly”. In addition, an operation of bonding, to one surface of anelectrolyte membrane already having a catalyst layer on the othersurface, a catalyst layer (only a catalyst layer, or a gas diffusionelectrode or the like) is also included in the “manufacture of amembrane-catalyst assembly”.

[Electrolyte Membrane]

The electrolyte membrane used in the method of manufacturing amembrane-catalyst assembly and the device for manufacturing amembrane-catalyst assembly of the present invention has protonconductivity. The electrolyte membrane is not particularly limited aslong as it operates as an electrolyte membrane used in polymerelectrolyte fuel cells, solid polymer electrolyte membrane waterelectrolyzers, electrochemical hydrogen pumps and the like, and may be aknown or commercially available product. The electrolyte membrane usedmay be a fluorine-based electrolyte membrane made of perfluorosulfonicacid or a hydrocarbon-based electrolyte membrane made of ahydrocarbon-based polymer obtained by imparting proton conductivity to ahydrocarbon-based skeleton.

In particular, a hydrocarbon-based electrolyte membrane has a higherglass transition temperature and larger shrinkage deformation duringheating than those of a fluorine-based electrolyte membrane, and it isoften difficult to find transfer conditions with excellent productivityin common thermocompression bonding methods. Therefore, themanufacturing method and the manufacturing device of the presentinvention can be preferably applied to a hydrocarbon-based electrolytemembrane.

[Catalyst Layer]

The catalyst layer used in the method of manufacturing amembrane-catalyst assembly and the device for manufacturing amembrane-catalyst assembly of the present invention is not particularlylimited as long as it operates as a catalyst layer used in polymerelectrolyte fuel cells, solid polymer electrolyte membrane waterelectrolyzers, electrochemical hydrogen pumps and the like. In general,it is possible to use a catalyst layer having a porous structure andincluding conductive particles such as carbon particles, catalystparticles supported on the conductive particles, such as platinumparticles or platinum alloy particles, and an electrolyte componenthaving proton conductivity, such as an ionomer.

Examples of preferable conductive particles include particles of carbonmaterials such as oil furnace black, gas furnace black, acetylene black,thermal black, graphite, carbon nanotubes, and graphene, and metaloxides such as tin oxide. Examples of preferable catalyst particlesinclude particles of single noble metals such as platinum, iridium,ruthenium, rhodium, and palladium, alloys of manganese, iron, cobalt,nickel, copper, zinc or the like with platinum, and ternary alloys ofthese metals with platinum and ruthenium. Examples of a preferableelectrolyte component include perfluorocarbon sulfonic acid-basedpolymers such as Nafion (registered trademark, manufactured by TheChemours Company), Aquivion (registered trademark, manufactured bySolvay Specialty Polymers), FLEMION (registered trademark, manufacturedby Asahi Glass Co., Ltd.), Aciplex (registered trademark, manufacturedby Asahi Kasei Corporation), and Fumion F (registered trademark,manufactured by FuMA-Tech GmbH), and hydrocarbon-based polymers such aspolysulfone sulfonic acid, polyaryletherketone sulfonic acid,polybenzimidazole alkylsulfonic acid, polybenzimidazole alkylphosphonicacid, polystyrene sulfonic acid, polyetheretherketone sulfonic acid, andpolyphenyl sulfonic acid.

The catalyst solution is not particularly limited as long as it is asolution containing these catalyst layer materials dispersed in asolvent that evaporates by drying, and is capable of forming thecatalyst layer on the electrolyte membrane. In general, the solvent usedis preferably water, an alcohol such as methanol, ethanol, 1-propanol,2-propanol, tert-butanol, or ethylene glycol, or N,N-dimethylformamideor N-methyl-2-pyrrolidone.

[Liquid Application Step]

The liquid application step is a step of applying a liquid to a surfaceof the catalyst layer before bonding, that is, a joint surface of thecatalyst layer to the electrolyte membrane. The term “application of aliquid” means to produce a state in which the liquid is attached to thesurface of the catalyst layer in an exposed state. It is desirable toprevent the liquid from substantially permeating into the catalystlayer. If the liquid permeates into the catalyst layer, the electrolytecomponent in the catalyst layer dissolves to reduce the strength of thecatalyst layer, so that cracks are likely to occur in thethermocompression bonding step. Further, in the case of a catalyst layerpreliminarily supported on a base material, if the liquid permeates intothe catalyst layer and reaches the interface between the catalyst layerand the base material, the releasability of the catalyst layer from thebase material may deteriorate.

In the liquid application step, the liquid is not particularly limitedas long as it is a material that evaporates by heating in the subsequentthermocompression bonding step and has no toxicity to the electrolytemembrane and the catalyst layer. For example, water, alcohols such asmethanol, ethanol, 1-propanol, 2-propanol, and tert-butanol, andmixtures thereof can be used, but it is desirable to use a liquidcontaining at least water. If the liquid undergoes a sudden temperaturechange during thermocompression bonding, wrinkles may occur in theelectrolyte membrane. However, a water-containing liquid can preventsuch damages because water has a higher boiling point and a higherspecific heat than those of the above-mentioned alcohols, and undergoesa gradual temperature rise during thermocompression bonding. Further,since water has a lower capability of permeating into the catalyst layerthan alcohols do, it is possible to prevent the occurrence of cracks dueto the permeation of the liquid into the catalyst layer. Moreover, useof the water-containing liquid enables to carry out the presentinvention at low cost, and can also reduce the environmental load of themanufacture. Even if the liquid remains in the membrane-catalystassembly manufactured by the manufacturing method or the manufacturingdevice of the present invention, the liquid does not have any effect onthe performance the equipment in which the liquid is used as long as theliquid is water. In the water-containing liquid, the content rate ofwater is more preferably 50 mass % to 100 mass %, still more preferably90 mass % to 100 mass %, and even more preferably 100 mass %. In otherwords, it is most preferable to use pure water as the liquid. Herein,“pure water” is high-purity water that does not contain impurities, andrefers to water at a level of grade A4 of JIS K0557(1998) that iscollected through a reverse osmosis membrane and an ion exchange resinand obtained using a commercially available pure water productionmachine, or water of the equivalent quality.

The liquid may contain a solid material in a dissolved or dispersedstate as long as the liquid has fluidity as a whole and provides theeffects of the present invention.

In the liquid application step, the liquid application method is notparticularly limited, and examples of the method include a method offorming a uniform coating film on the surface of the catalyst layerusing a gravure coater, a die coater, a comma coater, or the like, amethod of immersing a catalyst transfer sheet in a liquid tankcontaining the liquid, and a method of applying the liquid to thesurface of the catalyst layer in a droplet form. The method of applyingthe liquid to the surface of the catalyst layer in a droplet form isparticularly preferable. Herein, the term “droplet form” refers to astate in which innumerable droplets are attached to the surface of thecatalyst layer. The term “droplets” refers to, among masses of theliquid aggregated by surface tension, masses having a size of 1 cm² orless on the catalyst layer. In the case where the liquid is applied inthe droplet form, it is possible to uniformly apply the minimumnecessary amount of the liquid for softening the electrolyte membrane tothe joint surface. Note that the applied droplets are “uniform” meansthat the total amount of the liquid applied per 1 cm² of the jointsurface is the same at any position in the joint surface. Further, evena liquid that tends to repel the catalyst layer and hardly forms auniform coating film, such as water, can be easily applied in a dropletform. Further, in the case where the liquid is in a droplet form, thearea of contact between the liquid and the catalyst layer is small, sothat it is possible to minimize the permeation of the liquid into thecatalyst layer before the thermocompression bonding. Since the dropletsare spread on the interface and unite with the neighboring droplets dueto the compression in the thermocompression bonding step, it is possibleto soften the electrolyte membrane at the whole interface.

In the liquid application step, it is preferable to apply the liquid sothat the amount of liquid at the start of compression bonding in thethermocompression bonding step may be 0.1 μL or more and 5 μL or lessper 1 cm² of the surface of the catalyst layer. If the amount of liquidin the thermocompression bonding step is less than 0.1 μL per 1 cm², theelectrolyte membrane may not be sufficiently softened and adhesion maybe insufficient, or part of droplets may not unite with each other bythe compression in the thermocompression bonding step, and some parts ofthe electrolyte membrane will not be softened. If the amount of liquidexceeds 5 μL per 1 cm², the liquid may drip during transportation, ornot substantially the total amount of the liquid evaporates by theheating during thermocompression bonding, so that the electrolytemembrane may swell due to the liquid remaining at the interface at themoment the compression is released. The amount of liquid is morepreferably 0.1 μL or more and 0.8 μL or less per 1 cm² of the surface ofthe catalyst layer. The amount of liquid can be measured by attaching,to the surface of the catalyst layer of the catalyst transfer sheet, asample piece such as a PET film piece whose weight has been measured soas to stack the sample piece on the catalyst layer, applying the liquidto the catalyst layer in the liquid application step, removing thesample base material with the liquid immediately before the sample piececomes into contact with the electrolyte membrane in thethermocompression bonding step and measuring the weight of the samplebase material with the liquid, and calculating the volume of the liquidper 1 cm² from the weight difference. The sample piece in themeasurement may be a square piece with a side of 1 cm to 10 cm.

Further, the smaller the average diameter of the applied droplets is,the more preferable it is. More specifically, the average diameter ofthe droplets is preferably 300 μm or less in a state where the dropletsare attached to the base material. The smaller the average diameter ofthe droplets is, the shorter the distance between the droplets is, sothat the droplets can unite with each other with a smaller amount ofliquid during compression in the thermocompression bonding step.

In the liquid application step, the means for applying the liquid in adroplet form is not particularly limited, and examples of the usablemeans include a method of spraying the droplets by a sprayer or inkjet,a method of condensing the droplets on the joint surface in a humidifiedatmosphere, and a method of spraying the liquid in a mist form using anultrasonic transducer or the like. The method of spraying the dropletsby a sprayer is preferable from the viewpoint that the liquid can beefficiently applied with the amount of liquid being controlled. Thesprayer for spraying the droplets is not particularly limited, and atwo-fluid spray nozzle or the like that is used to atomize and spray theliquid by compressed air can be used.

[Thermocompression Bonding Step]

The catalyst layer that has been subjected to the liquid applicationstep is then subjected to a thermocompression bonding step in which thecatalyst layer is thermocompression-bonded to the electrolyte membrane.The thermocompression bonding step is a step of bonding the catalystlayer to the electrolyte membrane by heating and compressing thecatalyst layer and the electrolyte membrane in a stacked state in whichthe surface of the catalyst layer to which the liquid is applied is incontact with the electrolyte membrane.

In the thermocompression bonding step, the time from when the catalystlayer comes into contact with the electrolyte membrane until thecompression force acts on the catalyst layer and the electrolytemembrane is desirably 0.1 seconds or less. If the time is longer than0.1 seconds, the electrolyte membrane is likely to swell due to adhesionof the liquid, whereas when the time is 0.1 seconds or less, swelling isprevented because the adhesion of the liquid and the fixation of theelectrolyte membrane by thermocompression bonding proceed substantiallyat the same time.

The heating temperature in the thermocompression bonding step is notparticularly limited, but is preferably equal to or higher than theboiling point of the liquid applied to the catalyst layer (hereinafterreferred to as the “boiling point of the liquid”) and 220° C. or less.The heating temperature is the maximum temperature at the joint surfacebetween the electrolyte membrane and the catalyst layer during thethermocompression bonding step, and can be measured using athermocouple. If the heating temperature is equal to or lower than theboiling point of the liquid, it takes time to evaporate the liquid andthe productivity is reduced. Alternatively, if the heating temperatureexceeds 220° C., the electrolyte membrane may be damaged by heat. Theheating temperature in the thermocompression bonding step is morepreferably equal to or higher than the boiling point of the liquid and160° C. or less. The term “boiling point of the liquid” refers to theboiling point at an external pressure of 1 atm. When the liquid to beevaporated has a single composition, the term means the boiling point ofthe liquid. When the liquid to be evaporated is a mixture, the termmeans the highest boiling point among those of the single components inthe mixture.

The pressure applied to the electrolyte membrane and the catalyst layerin the thermocompression bonding step may be appropriately set, but ispreferably 1 MPa or more and 20 MPa or less. If the pressure is lessthan 1 MPa, the electrolyte membrane and the catalyst layer may not besufficiently adhered to each other. If the pressure exceeds 20 MPa,excessive pressure may be applied to the catalyst layer and theelectrolyte membrane, so that the structure of the catalyst layer may bedestroyed, and mechanical damage to the electrolyte membrane mayincrease, resulting in deterioration of durability and power generationperformance. The pressure in the thermocompression bonding step is morepreferably 1 MPa to 10 MPa.

The form of compression in the thermocompression bonding step is notparticularly limited, and may be a mode of a line contact in which theelectrolyte membrane and the catalyst layer come into contact with eachother in a single line form as with a hot press roll, or a mode of asurface contact in which the electrolyte membrane and the catalyst layercome into contact with each other in a plane form over a certain widthin the transport direction as with a double-belt pressing mechanism.

The manufacturing method of the present invention has been describedabove, and as can be easily understood from the above description andthe following description of embodiments, the present specification alsodiscloses a manufacturing device as described below for carrying out themanufacturing method.

(1) A device for manufacturing a membrane-catalyst assembly including anelectrolyte membrane and a catalyst layer bonded to the electrolytemembrane, the device including:

a liquid applicator that applies a liquid to a surface of the catalystlayer before bonding; and

a thermocompression bonding unit that bonds, to the electrolytemembrane, the catalyst layer to which the liquid is applied bythermocompression bonding.

(2) The device according to the item (1), wherein the liquid applicatorapplies the liquid to the surface of the catalyst layer in a dropletform.

(3) The device according to the item (2), wherein the liquid applicatoris a sprayer.

Hereinafter, specific embodiments of the present invention will bedescribed with reference to schematic diagrams of the manufacturingdevice for achieving the manufacturing method of the present invention.It is to be noted that the following description is provided forfacilitating the understanding of the present invention, and does notlimit the present invention in any way. However, as can be easilyunderstood by those skilled in the art, references to preferable aspectsand variations in individual embodiments are to be interpreted asdescriptions of the manufacturing method or the manufacturing device ofthe present invention as a superordinate concept. In the presentspecification, the upper part of each drawing is referred to as “upper”and the lower part thereof is referred to as “lower” for convenience,but the vertical direction of each drawing does not necessarily mean thevertical direction from the ground.

First Embodiment: Manufacture of Catalyst Layer-Attached ElectrolyteMembrane—1

FIG. 1 is a side view showing a schematic configuration of a device formanufacturing a catalyst layer-attached electrolyte membrane, which isone embodiment of a device for manufacturing a membrane-catalystassembly of the present invention.

In a device 100 for manufacturing a membrane-catalyst assembly accordingto this embodiment, a catalyst layer-attached electrolyte membrane ismanufactured as follows.

An electrolyte membrane 10 is unwound from an electrolyte membranesupply roll 11, and supplied to a thermocompression bonding section Pthrough a guide roll 12. Catalyst transfer sheet supply rolls 21A and21B are provided above and below the unwound electrolyte membrane 10,respectively. A catalyst layer to be bonded to the upper surface of theelectrolyte membrane 10 is formed using a catalyst transfer sheet 20A.The catalyst transfer sheet 20A is produced by preliminarily applying acatalyst solution to a sheet serving as a base material, for example.The catalyst transfer sheet 20A is unwound from the catalyst transfersheet supply roll 21A in a state where the base material supports thecatalyst layer, and is transported through a backup roll 31A and a guideroll 22A in this order with the base material side reverse to thecatalyst layer-formed surface of the catalyst transfer sheet 20A beingsupported on the rolls. (Since the base material is separated after thecatalyst layer and the electrolyte membrane are bonded together, it isalso called a temporary base material.) A catalyst transfer sheet 20Bfor forming a catalyst layer on the lower surface of the electrolytemembrane 10 is unwound from the catalyst transfer sheet supply roll 21B,and is transported through a backup roll 31B and a guide roll 22B inthis order with the base material side of the catalyst transfer sheet20B being supported on the rolls. In this way, the catalyst transfersheets 20A and 20B are supplied to the thermocompression bonding sectionP so that the surfaces of the catalyst transfer sheets 20A and 20B onwhich the catalyst layers are formed may face the electrolyte membrane10.

The material of the base material of the catalyst transfer sheets 20Aand 20B is not particularly limited, and may be a hydrocarbon-basedplastic film typified by those of polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP),polyimide, and polyphenylene sulfide, or a fluorine-based film typifiedby those of perfluoroalkoxy alkane (PFA), polytetrafluoroethylene(PTFE), and an ethylene-tetrafluoroethylene copolymer (ETFE).

It is more preferable that the base material have air permeability.Having air permeability means to have a property of being capable ofpermeating gases, and examples of a case where the base material has airpermeability include a case where the base material has porescommunicating in the thickness direction thereof. Use of a base materialhaving air permeability enables to effectively discharge the liquidvapor generated during thermocompression bonding even when the basematerial is still bonded to the catalyst layer. The base material havingair permeability may be, for example, a porous material formed from theabove-mentioned material.

For the guide rolls 12, 22A, and 22B, it is preferable to use anexpander roll in order to eliminate wrinkles and slacks of theelectrolyte membrane 10 and the catalyst transfer sheets 20A and 21Bsupplied to the thermocompression bonding section P.

The device 100 for manufacturing a membrane-catalyst assembly accordingto this embodiment is configured to transfer the catalyst layer to eachof both surfaces of the electrolyte membrane 10, but may be configuredto transfer the catalyst layer to only one surface of the electrolytemembrane 10.

In this embodiment, a spray nozzle 30A is provided so as to face thecatalyst transfer sheet 20A supported on the backup roll 31A. The spraynozzle 30A has a discharge port directed toward the central axis of thebackup roll 31A, and is provided at a position separated from the backuproll 31A by a predetermined distance. At least one spray nozzle 30A isprovided in the width direction of the catalyst transfer sheet 20A inaccordance with the width of the base material of the catalyst transfersheet 20A.

The spray nozzle 30A discharges water supplied from a water supply tank(not shown) from the discharge port to apply droplets to the jointsurface of the catalyst layer to the electrolyte membrane.

Further, the spray nozzle 30A and a space S in which the droplets fromthe discharge port of the spray nozzle 30A fly to the catalyst layer aresurrounded by a nozzle chamber 32A. To the nozzle chamber 32A, apressure reducing tank 34A for reducing the pressure in the space S isconnected by piping via a valve 33A for switching to pressure reduction.Since the pressure reducing tank 34A makes the space S have a negativepressure relative to the environmental pressure of the manufacturingdevice, the outside air is slightly sucked into the space S from the gapprovided between the nozzle chamber 32A and the catalyst transfer sheet20A, and excess droplets from the spray nozzle 30A are prevented fromscattering around. The water collected in the nozzle chamber 32A isdischarged from a drain (not shown) provided in the nozzle chamber 32A,and returned to the water supply tank and reused.

The above-mentioned description is a description of the liquidapplicator for the catalyst transfer sheet 20A, and the description ofthe liquid applicator (a spray nozzle 30B, a nozzle chamber 32B, a valve33B, and a pressure reducing tank 34B) provided for the catalysttransfer sheet 20B is omitted because the latter liquid applicator has asimilar configuration to that of the former liquid applicator.

In this way, the electrolyte membrane 10, and the catalyst transfersheets 20A and 20B with the liquid applied to the joint surfaces to theelectrolyte membrane 10 are supplied to the thermocompression bondingsection P, and pass between hot press rolls 40A and 40B. As shown inFIG. 8 , it is preferable to provide heat shield plates 41A and 41Bbetween the catalyst transfer sheet 20A and the hot press roll 40A andbetween the catalyst transfer sheet 20B and the hot press roll 40B,respectively. Providing the heat shield plates 41A and 41B prevents theliquid applied to the catalyst transfer sheets 20A and 20B fromevaporating before the heat pressing due to the radiant heat radiatedfrom the hot press rolls 40A and 40B.

The hot press rolls 40A and 40B are connected to a driving unit (notshown), and can rotate at a controlled speed. The hot press rolls 40Aand 40B rotate at a constant speed while applying heat and pressure tothe electrolyte membrane 10 and the catalyst transfer sheets 20A and20B. Accordingly, the hot press rolls 40A and 40B, while transportingthe electrolyte membrane 10 and the catalyst transfer sheets 20A and 20Bat a synchronized transport speed, thermocompression-bond the catalystlayer to each of both surfaces of the electrolyte membrane 10 to form amembrane-catalyst layer assembly 13 a. For the hot roll presses 40A and40B, the heating device, pressurizing device, and the like are notshown.

The materials of the hot press rolls 40A and 40B are not particularlylimited, but it is desirable that one of the rolls be made of a metalsuch as stainless steel, and the other roll have a structure in whichthe roll is covered with a surface layer made of an elastic body such asa resin or an elastomer material typified by a rubber. In the case of acombination of metal rolls, the contact width for compression is toosmall and the compression time required for bonding may not be secured,or the electrolyte membrane 10 and the catalyst transfer sheets 20A and20B may not be uniformly compressed in the width direction.Alternatively, in the case of a combination of rolls covered with asurface layer made of a rubber, the heat is poorly transferred and itmay be difficult to sufficiently heat the electrolyte membrane and thecatalyst layers. It is possible to sufficiently heat the electrolytemembrane and the catalyst layers with one of the hot press rolls 40A and40B made of a metal, and to maintain a satisfactory line contact betweenthe electrolyte membrane and the catalyst layers and uniformize the linepressure in the width direction of the base material with the otherpress roll having a surface layer made of an elastic body, because thepress roll flexibly changes the shape following the catalyst transfersheets 20A and 20B.

As for the material of the elastic body, when a rubber is used, examplesof usable materials include a fluororubber, a silicon rubber, an EPDM(ethylene-propylene-diene rubber), neoprene, a CSM (chlorosulfonatedpolyethylene rubber), a urethane rubber, a NBR (nitrile rubber), andebonite. It is preferable that the elastic body have a rubber hardnessin the range of 70 to 97° according to the Shore A standard. If thehardness is less than 70°, the amount of deformation of the elastic bodyis large, and the contact width for compression with the catalysttransfer sheets 20A and 20B is too large, so that the pressure requiredfor bonding the electrolyte membrane 10 to the catalyst layers may notbe secured. Conversely, if the hardness exceeds 97°, the amount ofdeformation of the elastic body is small, and the contact width forcompression is too small, so that the compression time required forbonding may not be secured.

The means for heating the hot press rolls 40A and 40B is notparticularly limited, and various heaters, and heat media such as steamand oil can be used. Further, the heating temperature may be the same ordifferent for the upper and lower rolls.

The method of controlling the compression force of the hot press rolls40A and 40B is not particularly limited, and the compression force maybe controlled using a pressurizing unit such as a hydraulic cylinder, ormay be controlled in accordance with the size of a gap provided betweenthe hot press rolls 40A and 40B, which is adjusted to a certain sizethrough position control using a servomotor or the like.

In this embodiment, the hot press rolls 40A and 40B as a line contactmechanism are used in the thermocompression bonding section P, but thepresent invention is not limited thereto. The mechanism may be amechanism for compressing the electrolyte membrane 10 and the catalysttransfer sheets 20A and 20B by a plurality of line contacts using aplurality of rolls, or a double-belt pressing mechanism for compressingthe electrolyte membrane 10 and the catalyst transfer sheets 20A and 20Bby a surface contact. When a plurality of pairs of rolls are used, thenumber of rolls provided is not particularly limited, but is preferably2 to 10 pairs.

In this way, the electrolyte membrane 10 and the catalyst transfersheets 20A and 20B pass through the thermocompression bonding section P,and the catalyst layer is transferred to each of both surfaces of theelectrolyte membrane 10, whereby the membrane-catalyst assembly(catalyst layer-attached electrolyte membrane) 13 a is formed.

Then, temporary base materials 24A and 24B are separated from themembrane-catalyst assembly 13 a as a catalyst layer-attached electrolytemembrane.

When the temporary base materials 24A and 24B have air permeability, theseparation method is not particularly limited. For example, thetemporary base materials 24A and 24B can be separated while themembrane-catalyst assembly 13 a is passed between guide rolls 23A and23B. While the temporary base materials are present on the catalystlayers, the temporary base materials support the electrolyte membranewith the catalyst layers interposed between the temporary base materialsand the electrolyte membrane, so that an effect of preventing theelectrolyte membrane from swelling is obtained. Therefore, when it isdifficult to evaporate almost the total amount of the liquid only by thethermocompression bonding step, an additional drying step may beprovided to dry the liquid between the time when the electrolytemembrane 10 and the catalyst transfer sheets 20A and 20B pass throughthe thermocompression bonding section P and the time when the temporarybase materials are separated. When the temporary base materials 24A and24B do not have air permeability, it is preferable to separate thetemporary base materials 24A and 24B from the membrane-catalyst assembly13 a in such a manner that the temporary base material 24A is held bythe hot press roll 40A and the temporary base material 24B is held bythe hot press roll 40B as shown in FIG. 7 . When the temporary basematerials are separated immediately after thermocompression bonding andthe catalyst layers are exposed, it is possible to effectively dischargethe liquid vapor generated in the thermocompression bonding step.

The temporary base materials separated from the membrane-catalyst layerassembly 13 a pass over the guide rolls 23A and 23B, respectively, andwound up on temporary base material take-up rolls 25A and 25B,respectively. The membrane-catalyst assembly 13 a from which thetemporary base materials 24A and 24B have been separated is fed by afeeding roll 14 and wound into a roll by a take-up roll 15.

The feeding roll 14 can be connected to a driving unit (not shown), andit is possible to transport the electrolyte membrane 10 at a controlledspeed when the press rolls 40A and 40B do not compress the electrolytemembrane 10 and the catalyst transfer sheets 20A and 20B.

Second Embodiment: Manufacture of Membrane-Electrode Assembly—1

FIG. 2 is a side view showing a schematic configuration of a device formanufacturing a membrane-electrode assembly, which is one embodiment ofa device for manufacturing a membrane-catalyst assembly of the presentinvention.

In a device 101 for manufacturing a membrane-catalyst assembly accordingto the embodiment shown in FIG. 2 , a membrane-electrode assembly ismanufactured as follows. The description of the parts similar to thosein the first embodiment will be omitted.

In the second embodiment, instead of the catalyst transfer sheets usedin the first embodiment, gas diffusion electrodes 80A and 80B aresupplied from gas diffusion electrode supply rolls 81A and 81B,respectively. The gas diffusion electrode supply rolls 81A and 81B areprovided above and below an unwound electrolyte membrane 10,respectively. The gas diffusion electrode 80A to be bonded to the uppersurface of the electrolyte membrane 10 is unwound from the gas diffusionelectrode supply roll 81A, and is transported through a backup roll 31Aand a guide roll 22A in this order with the gas diffusion electrode basematerial side reverse to the catalyst layer-formed surface of the gasdiffusion electrode 80A being supported on the rolls. The gas diffusionelectrode 80B to be bonded to the lower surface of the electrolytemembrane 10 is unwound from the gas diffusion electrode supply roll 81B,and is transported through a backup roll 31B and a guide roll 22B inthis order with the gas diffusion electrode base material side reverseto the catalyst layer-formed surface of the gas diffusion electrode 80Bbeing supported on the rolls. In this way, the gas diffusion electrodes80A and 80B are supplied to a thermocompression bonding section P sothat the surfaces of the gas diffusion electrodes 80A and 80B on whichthe catalyst layers are formed may face the electrolyte membrane 10.

The electrolyte membrane 10, and the gas diffusion electrodes 80A and80B with a liquid applied to the joint surfaces to the electrolytemembrane 10 are supplied to the thermocompression bonding section P, andpass between hot press rolls 40A and 40B and bonded together to form amembrane-catalyst assembly (membrane-electrode assembly) 13 b. Themembrane-catalyst assembly 13 b as a membrane-electrode assembly is fedby a feeding roll 14 and wound into a roll by a membrane-catalystassembly take-up roll 15.

Third Embodiment: Manufacture of Catalyst Layer-Attached ElectrolyteMembrane—2

In the third embodiment, first, a first catalyst layer is formed on onesurface of an electrolyte membrane using a catalyst layer formingapparatus 102 shown in FIG. 3 . The first catalyst layer is formed asfollows.

In this embodiment, an electrolyte membrane 10′ in a state of beingsupported on a support is supplied to the catalyst layer formingapparatus 102. The material of the support for the electrolyte membraneis not particularly limited, but a PET film can be used, for example.

The electrolyte membrane 10′ with the support is unwound from anelectrolyte membrane supply roll 11, and supplied to a catalyst solutioncoater 72 through a guide roll 12. The catalyst solution coater 72 isprovided so as to face the electrolyte membrane 10′ supported on abackup roll 73. To the catalyst solution coater 72, a catalyst solutionis supplied from a catalyst solution tank 70 using a catalyst solutionfeeding pump 71, and the catalyst solution coater 72 forms a coatingfilm by applying the supplied catalyst solution to the electrolytemembrane. The method for applying the catalyst solution in the catalystsolution coater 72 is not particularly limited. Methods such as agravure coater, a die coater, a comma coater, a roll coater, a spraycoater, and a screen printing method can be employed.

Then, the coating film of the catalyst solution formed on theelectrolyte membrane is dried by a dryer 74, and the solvent in thecatalyst solution is evaporated to form a dried first catalyst layer.The method for drying the catalyst solution in the dryer 74 is notparticularly limited. A method of blowing a heat medium such as hot air,or a heat oven method using a heater can be employed.

A membrane-first catalyst layer assembly 16 including the electrolytemembrane and the first catalyst layer formed on the electrolyte membraneis fed by a feeding roll 14 and wound into a roll by a take-up roll 17with the support attached to the membrane-first catalyst layer assembly16.

Then, a second catalyst layer is formed on a surface of the electrolytemembrane reverse to the surface on which the first catalyst layer isformed using a device 103 for manufacturing a membrane-catalyst assemblyaccording to an embodiment shown in FIG. 4 . The second catalyst layeris formed as follows.

The membrane-first catalyst layer assembly 16 is unwound from a supplyroll 18 and passes on a guide roll 12, and a support 51 is separatedfrom the interface with the electrolyte membrane via guide rolls 26A and26B. The support 51 separated in this process is wound on a supporttake-up roll 50.

On a first catalyst layer surface of the membrane-first catalyst layerassembly 16 from which the support 51 has been separated, a cover film61 unwound from a cover film supply roll 60 is laminated via guide rolls27A and 27B, and then the membrane-first catalyst layer assembly 16 withthe cover film 61 is supplied to a thermocompression bonding section P.The cover film 61 may be laminated before the support 51 is separated.

The cover film 61 is used to protect the first catalyst layer during thestep of forming the second catalyst layer, and the material of the coverfilm 61 is not particularly limited as long as it does not interferewith the function of the catalyst layer by the attachment anddetachment. In general, it is possible to use natural fiber sheetstypified by paper, hydrocarbon-based plastic films typified by those ofpolyethylene terephthalate (PET), polyethylene naphthalate (PEN),polyethylene (PE), polypropylene (PP), polyimide, and polyphenylenesulfide, fluorine-based films typified by those of perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), and anethylene-tetrafluoroethylene copolymer (ETFE), and materials obtained byapplying an acrylic pressure-sensitive adhesive, a urethane acrylatepressure-sensitive adhesive, a rubber pressure-sensitive adhesive, asilicone pressure-sensitive adhesive or the like to the above-mentionedmaterials to improve adhesion to an adherend. A material having improvedadhesion also provides an effect of preventing the electrolyte membranefrom swelling because the material can support the electrolyte membranewhile the electrolyte membrane is in contact with the liquid.

To the membrane-first catalyst layer assembly 16 supplied to thethermocompression bonding section P, the second catalyst layer isthermocompression-bonded in a state where the first catalyst layer iscovered with the cover film by the liquid application step and thethermocompression bonding step similar to those in the first embodimentto form a membrane-catalyst assembly (catalyst layer-attachedelectrolyte membrane) 13 c.

The membrane-catalyst assembly 13 c as a catalyst layer-attachedelectrolyte membrane that has passed through the thermocompressionbonding section P passes between guide rolls 23A and 23B. During thepassage, a temporary base material 24A is separated from themembrane-catalyst layer assembly 13 c, and wound up on a temporary basematerial take-up roll 25A. The membrane-catalyst assembly 13 c fromwhich the temporary base material 24A has been separated is fed by afeeding roll 14 and wound into a roll by a catalyst layer-attachedelectrolyte membrane take-up roll 15. The membrane-catalyst assembly 13c may be wound up with the cover film 61 bonded thereto, or the coverfilm 61 may be separated from the membrane-catalyst assembly 13 c with ahot press roll 40B immediately after pressing. When themembrane-catalyst assembly 13 c is wound up with the cover film 61bonded thereto, it is possible to prevent wrinkles and elongation of thecatalyst layer-attached electrolyte membrane, and to protect thecatalyst layer from physical damages due to external factors. Further,when the cover film 61 is separated immediately after thermocompressionbonding and the catalyst layer is exposed, it is possible to effectivelydischarge the liquid vapor generated in the thermocompression bondingstep. In this case, the catalyst layer can be protected with a new coverfilm before the membrane-catalyst assembly 13 c is wound up.

Fourth Embodiment: Manufacture of Catalyst Layer-Attached ElectrolyteMembrane—3

In the fourth embodiment, first, a first catalyst layer is formed on onesurface of an electrolyte membrane using a device 104 for manufacturinga membrane-catalyst assembly according to an embodiment shown in FIG. 5. The first catalyst layer is formed as follows.

In this embodiment, an electrolyte membrane 10′ in a state of beingsupported on a support is supplied to the catalyst layer formingapparatus 104. The electrolyte membrane 10′ with the support is unwoundfrom an electrolyte membrane supply roll 11, and supplied to athermocompression bonding section P. To the electrolyte membrane 10′supplied to the thermocompression bonding section P, the first catalystlayer is thermocompression-bonded by the liquid application step and thethermocompression bonding step similar to those in the first embodimentto form a membrane-first catalyst layer assembly 16′.

The membrane-first catalyst layer assembly 16′ including the support anda temporary base material of a catalyst transfer sheet 20A is fed by afeeding roll 14 and wound into a roll by a take-up roll 17.

Then, a second catalyst layer is formed on a surface of the electrolytemembrane reverse to the surface on which the first catalyst layer isformed using a catalyst layer forming apparatus 105 according to anembodiment shown in FIG. 6 . The second catalyst layer is formed asfollows.

The membrane-first catalyst layer assembly 16′ is unwound from a supplyroll 18, and a support 51 is separated from the interface with theelectrolyte membrane via guide rolls 26A and 26B. The support 51separated in this process is wound on a support take-up roll 50.

On the membrane-first catalyst layer assembly 16′ from which the support51 has been separated, the second catalyst layer is formed by a catalystsolution coater 72 and a dryer 74 similar to those in the thirdembodiment to form a membrane-catalyst assembly (catalyst layer-attachedelectrolyte membrane) 13 d.

The membrane-catalyst assembly 13 d as a catalyst layer-attachedelectrolyte membrane is fed by a feeding roll 14, and themembrane-catalyst assembly 13 d including the temporary base material iswound into a roll by a catalyst layer-attached electrolyte membranetake-up roll 15.

EXAMPLES

Hereinafter, the present invention will be more specifically describedwith reference to examples, but the present invention is not limited tothese examples.

In Examples 1 to 6, a catalyst transfer sheet roll (width of basematerial: 100 mm, thickness: 8 μm) was used as a catalyst transfersheet. The catalyst transfer sheet roll was obtained by applying, to acontinuous band-shaped PTFE sheet as a base material, a catalyst coatingliquid containing a Pt-supported carbon catalyst TEC10E50E manufacturedby Tanaka Kikinzoku Kogyo K.K. and a Nafion (registered trademark)solution, then drying the catalyst coating liquid to give a catalysttransfer sheet, and forming the catalyst transfer sheet into a roll(amount of supported platinum: 0.3 mg/cm²).

The electrolyte membranes of Examples 2 to 6 were manufactured withreference to the manufacturing method described in Japanese PatentLaid-open Publication No. 2018-60789.

Example 1

Using a device having the schematic configuration shown in FIG. 1 , thecatalyst layer was transferred from the above-mentioned catalysttransfer sheet to one surface of a commercially available “Nafion(registered trademark)” membrane, trade name NR211 (thickness: 25 μm)used as an electrolyte membrane according to the method described in theabove-mentioned first embodiment.

In the liquid application step, 100% pure water was applied to thecatalyst layer in a droplet form in an amount of 0.4 μL per 1 cm² usinga flat spray nozzle CBIMV 80005S manufactured by H. IKEUCHI & CO., LTD.

In the thermocompression bonding step, a pair of hot press rolls eachhaving a diameter of 250 mm was used. One of the rolls was a stainlesssteel roll, and the other roll was a fluororubber roll having a hardnessof 90° (Shore A). The hot press rolls applied a pressure of 3.0 MPa. Thepressure is a value measured using a Prescale film manufactured byFUJIFILM Corporation. The rolls had a surface temperature of 160° C.,and the heating temperature measured with a thermocouple provided at thejoint interface was found to be 115° C. The electrolyte membrane and thecatalyst transfer sheet were transported at a transport speed of 4.0m/min.

As a result of visual evaluation of the obtained membrane-catalystassembly, there was no transfer failure of the catalyst layer norswelling or wrinkles of the electrolyte membrane, and themembrane-catalyst assembly was of high quality.

Example 2

Using a device having the schematic configuration shown in FIG. 1 , thecatalyst layer was transferred from the catalyst transfer sheet same asthe one used in Example 1 to one surface of a polyetherketone-basedpolymer electrolyte membrane made of a polymer represented by thefollowing formula (G1) according to the method described in theabove-mentioned first embodiment.

In the liquid application step, 100% pure water was applied to thecatalyst layer in an amount of 0.4 μL per 1 cm² using a flat spraynozzle CBIMV 80005S manufactured by H. IKEUCHI & CO., LTD.

In the thermocompression bonding step, a pair of hot press rolls eachhaving a diameter of 250 mm was used. One of the rolls was a stainlesssteel roll, and the other roll was a fluororubber roll having a hardnessof 90° (Shore A). The hot press rolls applied a pressure of 4.2 MPa. Thepressure is a value measured using a Prescale film manufactured byFUJIFILM Corporation. The rolls had a surface temperature of 160° C.,and the heating temperature measured with a thermocouple provided at thejoint interface was found to be 115° C. The electrolyte membrane and thecatalyst transfer sheet were transported at a transport speed of 4.0m/min.

As a result of visual evaluation of the obtained membrane-catalystassembly, there was no transfer failure of the catalyst layer norswelling or wrinkles of the electrolyte membrane, and themembrane-catalyst assembly was of high quality.

Example 3

Using a device having the schematic configuration shown in FIG. 1 , thecatalyst layer was transferred from the above-mentioned catalysttransfer sheet to one surface of a polyarylene-based polymer electrolytemembrane made of a polymer represented by the following formula (G2)according to the method described in the above-mentioned firstembodiment.

(In the formula (G2), k, m, and n are integers, and k is 25, m is 380,and n is 8.)

The liquid application step and the thermocompression bonding step wereperformed in the same manner as in Example 2.

As a result of visual evaluation of the obtained membrane-catalystassembly, there was no transfer failure of the catalyst layer norswelling or wrinkles of the electrolyte membrane, and themembrane-catalyst assembly was of high quality.

Example 4

Using a device having the schematic configuration shown in FIG. 1 , thecatalyst layer was transferred from the above-mentioned catalysttransfer sheet to one surface of a polyethersulfone-based polymerelectrolyte membrane including a segment represented by the followingformula (G3) and a segment represented by the following formula (G4)according to the method described in the above-mentioned firstembodiment.

(In the formulae (G3) and (G4), p, q, and r are integers, and p is 170,q is 380, and r is 4.)

The liquid application step and the thermocompression bonding step wereperformed in the same manner as in Example 2.

As a result of visual evaluation of the obtained membrane-catalystassembly, there was no transfer failure of the catalyst layer norswelling or wrinkles of the electrolyte membrane, and themembrane-catalyst assembly was of high quality.

Example 5

A catalyst layer-attached electrolyte membrane was manufacturedaccording to the method described in the above-mentioned thirdembodiment.

Using an apparatus having the schematic configuration shown in FIG. 3 ,a catalyst solution was applied to one surface of thepolyetherketone-based polymer electrolyte membrane made of the polymerrepresented by the formula (G1), and the catalyst solution was dried toform a first catalyst layer. The catalyst solution used was a catalystcoating liquid containing a Pt-supported carbon catalyst TEC10E50Emanufactured by Tanaka Kikinzoku Kogyo K.K. and a Nafion (registeredtrademark) solution. The catalyst solution was dried at 120° C. for 5minutes to give a catalyst layer having a thickness of 5 μm.

Then, using a device having the schematic configuration shown in FIG. 4, a second catalyst layer was transferred from the above-mentionedcatalyst transfer sheet to the other surface of thepolyetherketone-based polymer electrolyte membrane having the firstcatalyst layer to form the second catalyst layer. A cover film to belaminated on the first catalyst layer surface was Lumirror (registeredtrademark), a PET film manufactured by TORAY INDUSTRIES, INC. and havinga thickness of 75 μm. The liquid application step and thethermocompression bonding step were performed by a method similar tothat in Example 2.

When the cover film was separated from the obtained catalystlayer-attached electrolyte membrane, no deposits or the like wereobserved on the cover film. Further, as a result of visual evaluation ofthe obtained catalyst layer-attached electrolyte membrane, there was notransfer failure of the catalyst layer nor swelling or wrinkles of theelectrolyte membrane, and the catalyst layer-attached electrolytemembrane was of high quality.

Example 6

A catalyst layer-attached electrolyte membrane was manufacturedaccording to the method described in the above-mentioned fourthembodiment.

Using a device having the schematic configuration shown in FIG. 5 , thefirst catalyst layer was transferred from the above-mentioned catalysttransfer sheet to one surface of the polyetherketone-based polymerelectrolyte membrane made of the polymer represented by the formula(G1). The liquid application step and the thermocompression bonding stepwere performed by a method similar to that in Example 2.

Then, using an apparatus having the schematic configuration shown inFIG. 6 , a catalyst solution similar to that of Example 5 was applied tothe other surface of the electrolyte membrane having the first catalystlayer, and the catalyst solution was dried to form a second catalystlayer.

When the temporary base material was separated from the obtainedcatalyst layer-attached electrolyte membrane, no deposits or the likewere observed on the temporary base material. Further, as a result ofvisual evaluation of the obtained catalyst layer-attached electrolytemembrane, there was no transfer failure of the catalyst layer norswelling or wrinkles of the electrolyte membrane, and the catalystlayer-attached electrolyte membrane was of high quality.

Comparative Example 1

The catalyst layer was transferred from the same catalyst transfer sheetas that used in Example 1 to one surface of an electrolyte membrane inthe same manner as in Example 2 except that the liquid application stepwas not performed. As a result of visual evaluation of the obtainedmembrane-catalyst assembly, transfer failure of the catalyst layer wasobserved.

DESCRIPTION OF REFERENCE SIGNS

-   -   100, 101, 103, 104: Device for manufacturing membrane-catalyst        assembly    -   102, 105: Catalyst layer forming apparatus    -   10, 10′: Electrolyte membrane    -   11, 18: Electrolyte membrane supply roll    -   13 a, 13 b, 13 c, 13 d: Membrane-catalyst assembly    -   14: Feeding roll    -   15, 17: Membrane-catalyst assembly take-up roll    -   16, 16′: Membrane-first catalyst layer assembly    -   12, 22A, 22B, 23A, 23B, 26A, 26B, 27A, 27B: Guide roll    -   20A, 20B: Catalyst transfer sheet    -   21A, 21B: Catalyst transfer sheet supply roll    -   24A, 24B: Temporary base material    -   25A, 25B: Temporary base material take-up roll    -   30A, 30B: Spray nozzle    -   31A, 31B, 73: Backup roll    -   32A, 32B: Nozzle chamber    -   33A, 33B: Valve    -   34A, 34B: Pressure reducing tank    -   40A, 40B: Hot press roll    -   41A, 41B: Heat shield plate    -   50: Support take-up roll    -   51: Support    -   60: Cover film supply roll    -   70: Catalyst solution tank    -   71: Catalyst solution feeding pump    -   72: Coater    -   74: Dryer    -   80A, 80B: Gas diffusion electrode    -   81A, 81B: Gas diffusion electrode supply roll    -   P: Thermocompression bonding section    -   S: Space

The invention claimed is:
 1. A method of manufacturing amembrane-catalyst assembly including an electrolyte membrane and acatalyst layer bonded to the electrolyte membrane, the methodcomprising: a liquid application step of applying a liquid in dropletform to a surface of the catalyst layer to form a droplet coveredcatalyst layer; and a bonding step of thermocompression bonding thedroplet covered catalyst layer to the electrolyte membrane to form themembrane-catalyst assembly.
 2. The method according to claim 1, whereinthe liquid applied in the liquid application step is a water-containingliquid.
 3. The method according to claim 2, wherein the water-containingliquid contains water at a content rate of 90 mass % or more and 100mass % or less.
 4. The method according to claim 3, wherein the liquidapplied in the liquid application step is pure water.
 5. The methodaccording to claim 1, wherein in the liquid application step, the liquidis applied by a sprayer.
 6. The method according to claim 1, wherein inthe liquid application step, the liquid is applied so that the surfaceof the catalyst layer contains an amount of the liquid in a range of 0.1μL or more and 5 μL or less per 1 cm² of the surface of the catalystlayer.
 7. The method according to claim 1, wherein the electrolytemembrane is a hydrocarbon-based electrolyte membrane.
 8. The methodaccording to claim 1, wherein the catalyst layer is supported on a basematerial before the bonding step and the base material has airpermeability.
 9. A method of manufacturing a catalyst layer-attachedelectrolyte membrane including an electrolyte membrane and a catalystlayer bonded to each of both surfaces of the electrolyte membrane, themethod comprising the steps of: applying a catalyst solution to a firstsurface of the electrolyte membrane and drying the catalyst solution toform a first catalyst layer; and bonding a second catalyst layer to asecond surface of the electrolyte membrane to form a second catalystlayer by a method comprising: a liquid application step of applying aliquid to a first surface of a catalyst layer to form a liquid coveredcatalyst layer; and a bonding step of thermocompression bonding theliquid covered catalyst layer to the second surface of the electrolytemembrane to form a second catalyst layer thereon.
 10. The methodaccording to claim 9, further comprising a step of covering the firstcatalyst layer with a cover film after its formation on the electrolytemembrane first surface and before the second catalyst layer is bonded tothe second surface of the electrolyte membrane.